Model-based analysis of treatment effects of paclitaxel microspheres in a microscopic peritoneal carcinomatosis model in mice

Purpose Paclitaxel (PTX)-loaded genipin-crosslinked gelatin microspheres (GP-MS) are a prolonged IP delivery system under development for the treatment of peritoneal minimal residual disease (pMRD). Here, we show the use of a pharmacokinetic-pharmacodynamic (PKPD) modelling approach to inform the formulation development of PTX-GP-MS in a mice pMRD model. Methods PTX blood concentrations and survival data were obtained in Balb/c Nu mice receiving different single IP doses (7.5 and/or 35 mg/kg) of PTX-ethanolic loaded GP-MS (PTX EtOH -GP-MS), PTX-nanosuspension loaded GP-MS (PTX nano -GP-MS), and immediate release formulation Abraxane®. A population PK model was developed to characterize the PTX blood concentration pattern and to predict PTX concentrations in peritoneum. Afterwards, PKPD relationships between the predicted peritoneal or blood concentrations and survival were explored using time-to-event modelling. Results A PKPD model was developed that simultaneously describes the competing effects of treatment efficacy (driven by peritoneal concentration) and toxicity (driven by blood concentration) of PTX on survival. Clear survival advantages of PTX nano -GP-MS over PTX EtOH -GP-MS and Abraxane® were found. Simulations of different doses of PTX nano -GP-MS demonstrated that drug-induced toxicity is high at doses between 20 and 35 mg/kg. Conclusions The model predicts that the dose range of 7.5-15 mg/kg of PTX nano -GP-MS provides an optimal balance between efficacy and safety.